Long Term Evolution Advanced (LTE-Advanced) (3GPPP LTE Release 10 & beyond) is a 4th Generation (4G) mobile communication system enhancing the basic LTE technology specified in 3GPP Release 8. Carrier Aggregation (CA) is among the multiple features introduced with LTE-Advanced. In order to increase bandwidth and thereby bitrate, an LTE-Advanced capable terminal or user equipment (UE) can be allocated downlink (DL) and uplink (UL) aggregated resources comprising two or more carriers, wherein aggregated carriers are referred to as Component Carriers (CC).
Three different modes of CA are defined within LTE-Advanced: (1) intra-band contiguous CA; (2) intra-band non-contiguous CA; and (3) inter-band CA. Intra-band CA relates to carrier aggregation wherein the component carriers belong to the same operating frequency band. For contiguous CA, contiguous component carriers are allocated while for non-contiguous CA carriers are allocated with one or more gaps between them. In case of inter-band CA, the component carriers belong to different operating frequency bands.
A component carrier can have a bandwidth of 1.4, 3, 5, 10, 15 or 20 Megahertz (MHz) and it is envisaged that a maximum of five component carriers can be aggregated, resulting in a maximum aggregated bandwidth of 100 MHz instead of at most 20 MHz without CA. However, according to Release 11 the maximum number of carriers in DL is 2, i.e. 2DL CA and therefore maximum aggregated bandwidth is 40 MHz. As an example, 3GPP TS 36.101 version 11.6.0 Release 11 may be consulted for further details on required UE transmission and reception characteristics.
It is envisaged that more than two, i.e. three downlink carrier aggregation (3DL CA), four downlink carrier aggregation (4DL CA), or five downlink carrier aggregation (5DL CA) will be introduced in the next releases to come. Current implementations are also restricted to one UL carrier, i.e. no CA on UL, while 2UL CA systems can be contemplated for future releases.
UEs can be said to support a specific functionality in case they have been tested accordingly to verify proper functioning. 3GPP TS 36.508 version 11.2.0, for example, defines a common test environment for UE conformance testing in Release 11 and 3GPP TS 36.521-1 version 11.2.0, Release 11 defines UE conformance specifications for radio transmission and reception for conformance testing including measurement procedures for the conformance tests. Test cases are defined for testing UE capabilities such as reference sensitivity level, maximum input level, adjacent channel selectivity, blocking characteristics, etc., wherein test cases are defined without taking the CA feature into account, i.e. a single carrier is established only, while other test cases measure the UE capabilities when CA is active, i.e. for 2DL CA in case of Release 11.
When performing state of the art carrier aggregation tests, so far, the entire test case had to be prepared beforehand. This means that the number of carriers, the protocols state of the individual carriers, the frequency bandwidth, etc. of the carriers all had to be set in advance, before the actual measurement could begin. This resulted in a low flexibility, since an operator of the measuring device could not on the fly change any of these settings without stopping the measurement and initiating a new measurement afterwards.
For example, the US-Patent Publication US 2014/0029440 A1 shows a state of the art carrier aggregation testing method and apparatus. This method and apparatus shows the above-mentioned disadvantages.
There is a need, therefore, for an approach that provides a measuring device and method, which allow for a very flexible measurement of the response of a device under test to carrier aggregation signals.